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<html>
<head>


    <meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Getting CSS Style Sheets</title>

<style type="text/css">
/*margin and padding on body element
  can introduce errors in determining
  element position and are not recommended;
  we turn them off as a foundation for YUI
  CSS treatments. */
body {
	margin:0;
	padding:0;
}
</style>

<link rel="stylesheet" type="text/css" href="../../build/fonts/fonts-min.css" />
<link rel="stylesheet" type="text/css" href="../../build/button/assets/skins/sam/button.css" />
<script type="text/javascript" src="../../build/yahoo-dom-event/yahoo-dom-event.js"></script>
<script type="text/javascript" src="../../build/element/element-min.js"></script>
<script type="text/javascript" src="../../build/button/button-min.js"></script>
<script type="text/javascript" src="../../build/get/get-min.js"></script>


<!--begin custom header content for this example-->
<style type="text/css" id="styleoverrides">
	
	#container .hd {
		background-image:url(http://l.yimg.com/a/i/us/nt/ma/ma_nws_1.gif);
		background-position:top right;
		background-repeat:no-repeat;
		background-color:none;
	} 
	
	#container h2 {
		border:none;
		margin-top:0;
	}

	#container h3 {
		color:#999999;
	}
	
	#buttonContainer {
		padding-bottom:.5em;
	}
	
	#container .module {
		padding:.5em 1em 1em 1em;
		overflow:hidden;
	}

/*

    When we load the new CSS files, these files will be loaded above this style block.
    If we need to override any styles supplied by the new CSS files, we can do this
    here.  For instance, this is useful if you are loading YUI skin files dynamically,
    but want to override some of the styles.

*/
</style>

<!--end custom header content for this example-->

</head>

<body class="yui-skin-sam">


<h1>Getting CSS Style Sheets</h1>

<div class="exampleIntro">
	<p><a href="http://developer.yahoo.com/yui/get">The YUI Get Utility</a> can be
used to fetch CSS stylesheets after the page has loaded.  This allows you to
reduce the size of your "main" stylesheet by segregating the style rules for
specific modules that may not be displayed when the page is first rendered.
Once the module is needed, you can bring in the CSS (and JavaScript)
dynamically using the Get Utility.</p>

<p>The example below demonstrates the dynamic addition and removal of three
stylesheets that change the appearance of the News module.  By clicking on the
buttons (which make use of the <a
href="http://developer.yahoo.com/yui/button/">YUI Button Control</a>), you can
add/remove border, background, and font treatments for the module.
(<strong>Note:</strong> The News module itself is built using the Get Utility
to fetch JSON data from the <a
href="http://developer.yahoo.com/search/news/V1/newsSearch.html">Yahoo! News
Search web service</a>; it follows the same code pattern described in the <a
href="get-script-basic.html">"Getting a Script Node with JSON Data"</a>
example.) </p>
			
</div>

<!--BEGIN SOURCE CODE FOR EXAMPLE =============================== -->

<div id="container">

    <div id="buttonContainer">
        <!--YUI Button instances, created from script, will go here.-->
    </div>

    <div class="module">
        <div class="hd"><h2>In the News:</h2></div>
        <div class="bd" id="results">
            <!--News stories will be displayed here.-->
        </div>
        <div class="ft">        
            <div id="searchControls">
                <!--Use a real form that works without JavaScript:-->
                <form method="GET" action="http://search.yahooapis.com/NewsSearchService/V1/newsSearch" id="newsSearch">            
                    <label for="searchString">Search Yahoo! News:</label> <input type="text" name="p" id="searchString" value="San Francisco" size="40">                
                    <input type="submit" id="getNewsData" value="Search Yahoo! News">                
                </form>            
            </div>
        </div>
    </div>
</div>

<script language="javascript">

// Encapsulating our code in a self-executing anonymous function
// is one way to create a namespace:
(function() {

// shortcuts and other variables:
var Button = YAHOO.widget.Button,
    Event = YAHOO.util.Event,
    Dom = YAHOO.util.Dom,
    Get = YAHOO.util.Get,
    elContainer = Dom.get("container"),
    tIds = {};

// YUI Buttons are attractive and effective for "call to action"
// tasks like the one here.  We'll create buttons purely from
// JavaScript; there's no need for this style-change functionality
// to be "accessible"; in fact, it's purely cosmetic, so keeping
// these buttons out of the page's initial DOM is preferable.  We'll
// use the "name" property of the button to determine what CSS to
// load when each button is clicked:
var borderButton = new Button({
    id: "borderButton",
    type: "checkbox",
    name: "border",
    label: "Border CSS",
    container: "buttonContainer" 
});
var backgroundButton = new Button({
    id: "backgroundButton",
    type: "checkbox",
    name: "background",
    label: "Background CSS",
    container: "buttonContainer"
});
var textButton = new Button({
    id: "textButton",
    type: "checkbox",
    name: "text",
    label: "Text CSS",
    container: "buttonContainer"
});
// Making available outside the anonymous function so these can be
// introspected in FireBug if desired:
YAHOO.example.buttons = [borderButton, backgroundButton, textButton];

// Checkbox buttons are either checked or unchecked; when their state
// changes, their "onCheckedChange" event fires.  We'll use that
// event to trigger the loading and unloading of CSS using the Get
// Utility.
var onCheckedChange = function() {
    //Which button was actuated?
    var name = this.get("name");
    //The button's checked state has already been updated, so if
    //true we load the necessary CSS:
    if(this.get("checked")) {
        // We'll use the 'data' parameter to pass through the name
        // of the CSS file to our onSuccess handler.  This allows
        // us to have access to the purge method when we want
        // to remove the CSS.
        //
        // In addition, we use the 'insertBefore' property to specify
        // the id of a style block we want to insert the new nodes
        // before.  By doing this, we can ensure that any style overrides
        // for the dynamically loaded CSS will be applied in the correct
        // order.
        Get.css("../get/assets/" + name + ".css", {
                data:         name,
                insertBefore: "styleoverrides",
                onSuccess:    onSuccess
        });
    } else {
        // In onSuccess, we save a reference to the callback object
        // in an associative array (tIds) indexed by the CSS name.  That 
        // allows us here, when the CSS needs to be removed, to simply
        // call the purge method corresponding to the item we want to 
        // remove.  Purge clears all the link nodes that were created
        // as part of the transaction (in this case, just a single 
        // link node).
        tIds[this.get("name")].purge();
        YAHOO.log("CSS was successfully purged; our object containing transaction ids now looks like this: " + YAHOO.lang.dump(tIds, 1),  "info", "example");
        
        // Some A-Grade browsers won't repaint automatically when CSS link nodes
        // are removed.  You can nudge these browsers to repaint by adding
        // a blank CSS stylesheet to the page:
        Get.css("../get/assets/neutral.css");
    }
};

// Now we can subscribe our onCheckedChange function to each
// of our three YUI Buttons' "checkedChange" event:
borderButton.on("checkedChange", onCheckedChange);
backgroundButton.on("checkedChange", onCheckedChange);
textButton.on("checkedChange", onCheckedChange);

// As noted above, in onSuccess we want to save the callback
// object in an associative array indexed by CSS file name so that
// we can purge the link nodes later if the CSS file needs to be
// removed.
var onSuccess = function(o) {
    tIds[o.data] = o;
    YAHOO.log("CSS was successfully returned; our object containing transaction ids now looks like this: " + YAHOO.lang.dump(tIds, 1), "info", "example");
}

})();
</script>

<script src="../get/assets/getNews.js" type="text/javascript"></script>

<!--END SOURCE CODE FOR EXAMPLE =============================== -->

</body>
</html>
